The invention relates to improvements in transmissions, and more particularly to improvements in transmissions which constitute or resemble so-called continuously variable transmissions (CVT). Still more particularly, the invention relates to improvements in apparatus which can be utilized to transmit variable torque in transmissions of the above outlined character and embody so-called torque sensors.
It is known to provide a continuously variable transmission with a mechanical or other suitable torque sensor which is (or can be) integrated into a pulley of the transmission. As a rule, the transmission comprises at least two pulleys which are mounted on discrete parallel shafts, and an endless flexible element (such as a belt or a chain) which is trained over the pulleys. Each pulley comprises a first conical flange which is rigidly affixed to (e.g., of one piece with) the respective shaft, and a second conical flange which is rotatable with the respective shaft and is movable axially of the shaft toward and away from the respective first flange. If the transmission comprises a torque sensor, such device serves to vary the pressure of a hydraulic fluid in at least one plenum chamber (which is adjacent the axially adjustable flange of one of the pulleys) as a function of variable torque being transmitted by the transmission.
The torque sensor can comprise rolling elements abutting cam faces provided on two components which are movable relative to each other; the rolling elements transmit torque which is being applied to the flanges of the corresponding pulley. The two components of the torque sensor move relative to each other (to thus influence fluid pressure in the at least one plenum chamber) in response to changes of the magnitude of torque being transmitted by the transmission and the resulting movements of the rolling elements along the cam faces.
A continuously variable transmission of the above outlined character is disclosed, for example, in published German patent application Serial No. 42 34 294 A1. This transmission comprises a torque sensor wherein one of the cam faces for the rolling elements (each of which is a sphere) is provided on a seal carrier; the latter is adjacent that side of an axially movable flange which faces away from the associated axially fixed flange of one of two pulleys forming part of the transmission. The seal carrier is adjacent and bounds a portion of a radially outer plenum chamber, namely the plenum chamber which confines the rolling elements of the torque sensor and contains a supply of fluid having a pressure corresponding to the torque being then transmitted by the transmission. The seal carrier further bounds a portion of a radially inner second plenum chamber. The pressure of fluid in the second plenum chamber is variable to thus select the ratio of the continuously variable transmission.
The other cam face for the rolling element or elements of the torque sensor disclosed in the aforementioned published German patent application is provided on a piston which is movable axially of the respective shaft and is outwardly adjacent the seal carrier (the latter is disposed between the piston and the axially movable flange of the respective pulley). The piston receives torque from a gear which mates with teeth provided on the piston. Axial movements of the piston result in controlled changes of the rate of fluid flow from a plenum chamber associated with that one of the aforementioned chambers which serves to determine the extent of frictional engagement between the flanges of the pulley and the adjacent surfaces of the endless flexible device (e.g., a chain).
In order to regulate the torque in dependency upon the selected transmission ratio, the rolling elements of the torque sensor are acted upon by an annular biasing member which urges them radially outwardly against the conical guide surface of a member which is rigidly secured to the axially movable flange of the respective pulley. The rolling elements are compelled to move radially inwardly and to roll along different portions of the properly configurated (three-dimensional) cam faces when the distance between the cam faces decreases.
A drawback of the aforedescribed continuously variable transmission is that the torque sensor and the mode of installing it in the transmission are quite complex and expensive. Thus, the number of discrete component parts is very high. Furthermore, the transmission is bulky, i.e., it occupies much room (as seen in the axial direction of its shafts) and a large number of its parts must be installed outside of the plenum chambers.
Another continuously variable transmission which embodies a torque sensor having spherical rolling elements between two cam faces in the form of ramps is disclosed in U.S. Pat. No. 5,295,915 granted Mar. 22, 1994 to Oswald Friedmann for xe2x80x9cCONTINUOUSLY VARIABLE SPEED TRANSMISSIONxe2x80x9d. U.S. Pat. No. 5,667,448 granted Sep. 16, 1997 to Oswald Friedmann for xe2x80x9cPOWER TRAINxe2x80x9d discloses a further continuously variable transmission, and a continuously variable transmission with a hydromechanical torque sensor is disclosed in U.S. Pat. No. 5,711,730 granted Jan. 27, 1998 to Oswald Friedmann et al. for xe2x80x9cTORQUE MONITORING APPARATUSxe2x80x9d. The disclosures of the German priority application Serial No. 198 50 527.2 filed Nov. 3, 1998, of the aforementioned published German patent application Serial No. 42 34 294 A1, and of all other US and foreign patents and patent applications identified in the present application are incorporated herein by reference.
An object of the invention is to provide a continuously variable transmission which employs an integrated torque sensor and is more compact and comprises fewer parts (i.e., it is less expensive) than heretofore known transmissions.
Another object of the invention is to provide an apparatus which embodies a novel and improved torque sensor and can be installed in a continuously variable transmission to achieve savings in space, a reduction of the overall number of parts and other important savings and improvements.
A further object of the invention is to provide a continously variable transmission with a novel and improved combination of parts which render it possible to take advantage of space that remains unoccupied in heretofore known continuously variable transmissions.
Still another object of the invention is to provide a novel and improved torque sensor which can be utilized in the power trains of motor vehicles or in other power trains which employ continuously variable transmissions.
A further object of the invention is to provide novel and improved pulleys for use in a transmission of the above outlined character.
Another object of the invention is to provide a motor vehicle wherein the power train embodies a continuously variable transmission of the above outlined character.
An additional object of the invention is to provide a continuously variable transmission wherein certain parts are capable of additional use in a motor vehicle or elsewhere.
One feature of the present invention resides in the provision of an apparatus which is constructed and assembled to transmit variable torque and comprises a shaft which is rotatable about a predetermined axis, a pulley including a first flange affixed to the shaft for axial and angular movements with the shaft and a second flange which is rotatable with the shaft but is movable relative to the shaft in the direction of the predetermined axis toward and away from the first flange, an endless flexible torque transmitting device (such as a chain or a belt) which is trained over the pulley, a fluid-containing plenum chamber at the second flange, and a torque sensor which is arranged to vary the pressure of fluid (such as oil) in the chamber in dependency upon the magnitude of the torque being transmitted by the improved apparatus. The torque sensor comprises first and second components having confronting cam faces (or analogous surfaces) and rolling elements disposed between the cam faces and serving to transmit torque which is being applied to the flanges. At least one of the aforementioned components of the torque sensor is movable relative to the other of these components in response to changes in the magnitude of transmitted torque. In accordance with an important and highly advantageous feature of the invention, the rolling elements and the cam faces are confined or disposed in the plenum chamber. This brings about substantial savings in space as considered in the axial direction of the pulley.
It will be seen that the torque sensor is or can be integrated into the pulley of the improved apparatus. The cam faces can be configurated in such a way that they effect a movement of the at least one component relative to the other component in response to rolling of the elements along at least one of the cam faces. The rolling elements can constitute spheres and the cam faces can extend in at least one of the directions including axially of the shaft and radialy of the axis.
The feature that the rolling elements are movable radially and/or axially of the shaft renders it possible to vary the pressure of fluid in the plenum chamber as a function of the torque being transmitted by the transmission as well as in dependency upon the speed ratio of the transmission, i.e., upon the axial distance between the flanges of the pulley.
The second flange can be provided with first and second guide surfaces which confine the rolling elements to movements radially of the axis of the pulley in response to movements of the second flange in the direction of the axis. Such construction and configuration of the second flange contribute to simplicity of the second flange and hence to greater simplicity of the entire pulley, i.e., to greater simplicity of the transmission (hereinafter also called CVT) which employs such pulley.
Alternatively, the first and second guide surfaces of the second flange can be designed to confine the rolling elements to movements in the direction of the axis of the pulley in response to movements of the second flange axially of the shaft. Such configuration of the second flange also cotributes to simplicity and reliability of the pulley and constitutes a presently preferred configuration of the second flange.
The second flange can comprise an annular portion having an external guide surface and extending in the direction of the axis of the shaft away from the first flange. Such apparatus can further comprise an annular member having an internal guide surface which surrounds the external guide surface. The guide surfaces flank the rolling elements and the annular member can be carried by the second flange. These just described features also contribute to simplicity, reliability, compactness and lower cost of the improved transmission.
The annular member can consist, at least in part, of a metallic sheet material (e.g., steel). Such annular member can be rigidly or rotatably connected to the second flange of the pulley.
The rolling elements can constitute spheres and the cam faces can be oriented to extend in at least one of the directions including axially of the shaft and radially of the axis of the shaft.
The other component of the torque sensor can include or constitute a carrier which is rigidly affixed to the shaft of the pulley and has a cylindrical external surface in sealing engagement with an annular member of the second flange. The shaft and the carrier bound at least a portion of the chamber and the at least one component of such torque sensor then comprises an annular piston which is movable in the plenum chamber in the direction of the axis of the pulley and is in sealing engagement with a cylindrical external surface of the carrier. An advantage of the just described embodiment is that it enhances the operativeness and the reliability of the improved transmission.
The just described embodiment of the apparatus can further comprise a first seal between the carrier and the annuar member at the cylindrical external surface and a second seal between the carrier of seals and the piston at the cylindrical internal surface of the carrier. The shaft and the piston preferably define a valve which serves to regulate the flow of fluid from the chamber as a function of the axial position of the piston relative to the shaft. The piston serves to take up an input torque of the apparatus and a presently preferred embodiment of the valve includes at least one outlet port which is provided in the shaft and communicates with the plenum chamber in at least one axial position of the piston relative to the shaft.
In accordance with a further modification, the piston comprises arms which are spaced apart from each other in a circumferential direction of the shaft and extend from the plenum chamber substantially radially outwardly and away from the axis of the pulley through openings which are provided in the aforementioned carrier of seals. Such apparatus preferably further comprises a gear having internal teeth mating with complementary external teeth of the arms; the gear is arranged to transmit torque to the piston and the piston is movable relative to the gear axially of the shaft of the pulley. The just described apparatus exhibits the advantage that it enhances the reliability of operation when the pressure of hydraulic fluid in the plenum chamber is relatively low or insufficient.
The openings can be dimensioned in such a way that the surfaces bounding the openings limit the extent of angular movability of the piston and the carrier relative to each other. More specifically, the surfaces bounding the openings limit the extent of movability of the arms (which are connected to the piston) and the carrier with respect to each other. The arms can contain or consist of a suitable metallic sheet material and can be welded or otherwise reliably bonded (e.g., soldered) to the piston. The arms and the gear can contain or consist of a metallic sheet material (e.g., sheet steel).
The carrier can comprise means for limiting the extent of movability of the piston relative to the shaft in the axial direction of the flange. Furthermore, the piston can be provided with an annular surface which is acted upon by the fluid in the plenum chamber adjacent the axially movable flange of the pulley and extends between the shaft and an annular internal extension or collar of the carrier (as seen radially of the axis of the pulley). To this end, the piston can be provided with a radially inner portion which sealingly engages the shaft and a radially outer portion which sealingly engages the carrer.
As already mentioned above, the first component of the torque sensor can comprise a piston which is installed in the plenum chamber and axially movably surrounds the shaft of the pulley. The piston is movable axially of the shaft of the pulley against the second flange in response to the application to the apparatus of an input torque in the absence of pressurized fluid in the chamber. The just described features of the improved apparatus contribute to lower cost of the pulley and they also enhance the simplicity and reliability of the transmission.
A further feature of the invention resides in the provision of a novel and improved variable-torque, variable speed ratio transmission. The latter comprises first and second adjustable rotary pulleys each having coaxial first and second flanges, an endless flexible torque transmitting device which is trained over the pulleys and is in force-transmitting engagement with the flanges, and means for adjusting at least one of the pulleys to select the magnitude of forces which act between the flanges of the at least one pulley and the endless flexible torque transmitting device as a function of the magnitude of transmitted torque. The adjusting means comprises a torque sensor having rolling elements and faces cooperating with the rolling elements to generate forces which vary in dependency upon variations of transmitted torque as well as upon variations of the speed ratio. The faces are configurated and oriented to effect a movement of the rolling elements at least substantially radially of the axis of the at least one pulley in response to changes of the speed ratio. The torque sensor is or can be integrated into the at least one pulley. The aforementioned faces are provided on two discrete components, and such components are caused to move relative to each other in response to movements of the rolling elements along the respective faces. As already pointed ot before, the rolling elements and the faces are preferably provided in a plenum chamber wherein the fluid urges the flanges of the at least one pulley against the adjacent portions of edge faces of the endless flexible torque transmitting device.
The arrangement is normally such that the means for transmitting torque (for example, the engine of a motor vehicle) is arranged to transmit torque to the first pulley and that the means for receiving torque from such transmission is connected to the second pulley.
The rolling elements can constitute (and preferably are) spheres.
The aforementioned faces can be configurated to effect a movement of the rolling elements substantially radially of the axis of the at least one pulley, as well as in the direction of such axis, in response to changes of the speed ratio.
Alternatively, the aforementioned faces can be provided on ramps which form part of the torque sensor, and the faces are inclined to provide for the rolling elements predetermined paths the inclination of which relative to the axis of the at least one pulley varies in the direction of movement of the rolling elements in response to changes of the speed ratio.
The rolling elements can include at least two spheres and the torque sensor can further comprise components defining for the two spheres two confronting grooves each of which has a substantially V-shaped configuration as seen in a direction radially of the axis of the at least one pulley. The components have contact surfaces which bound the grooves and are disposed at least substantially diametrically opposite each other. Each sphere is guided by a pair of contact surfaces which are at least substantially parallel to each other and tangential to the respective sphere, at least at a given radial distance from the axis of the at least one pulley.
The aforementioned faces can be arranged to transmit to the rolling elements forces each of which has at least one component acting radially of the axis of the at least one pulley. The arrangement is preferably such that the forces further have additional components acting in the axial direction of the at least one pulley. The magnitude of each at least one (radially acting) force component is or can be a relatively small (e.g., minute) fraction of the magnitude of a second component.
The engine or another suitable prime mover is preferably arranged to transmit torque to the at least one pulley (i.e., to the pulley which is combined with or embodies the torque sensor.
As a rule, the first flange of the at least one pulley is an axially fixed fange and the second flange of such pulley is then an axially movable flange. The torque sensor which is assocated with such pulley further includes a piston which is provided in a plenum chamber containing oil, transmission fluid or another hydraulic fluid and being adjacent the axially movable flange. The axially movable flange can be said to form part of a composite cylinder which defines the plenum chamber, and the piston is movable in the chamber in response to changes of the torque being transmitted by the torque sensor to thus select the magnitude of the force which the hydraulic fluid in the plenum chamber applies to the axially movable flange for transmission to the endless flexible torque transmitting device.
In the just outlined transmission wherein at least one pulley includes an axially fixed and an axially movable flange, the aforementioned faces are normally arranged to move the rolling elements substantially radially of and relative to the axially movable flange. The torque sensor of such transmission can but need not always further comprise cages for the rolling elements; if provided, the cages are movable along the guide faces for the rolling elements.
One of the faces can be provided on an at least partially conical carrier which is affixed to the axially movable flange of the at least one pulley, and such one face is or can be configurated to confine the rolling elements to movements at least substantially radially of the axis of the at least one pulley. The at least partially conical carrier can taper toward the axis of the at least one pulley in a direction away from the axially movable flange of the respective pulley.
In many instances, each of the pulleys comprises a rotary shaft (such shafts are normally parallel to each other); each first flange is normally rigid (e.g., of one piece) with the respective shaft, and each second flange is arraged to rotate with the respective shaft but is free to move axially of such shaft.
Still another feature of the present invention resides in the provision of a transmission (such as a CVT) having a plurality of speed ratios and comprising a first adjustable pulley which is rotatable about a first axis, a second adjustable pulley which is rotatable about a second axis (each pulley comprises a shaft defining the respective axis, a first flange which is rigid with the respective shaft, and a second flange which is arranged to rotate with and to move axially of the respective shaft toward and away from the corresponding first flange), an endless flexible torque transmitting device (preferably a link chain or the like) which is trained over the two pulleys, means for supplying torque to the shaft of the first pulley, means for receiving torque from the shaft of the second pulley, a cylinder and piston unit which is operable to move the second flange of one of the pulleys as a function of the speed ratio and of the magnitude of the torque being transmitted by the transmission, and means for operating the cylinder and piston unit. The operating means comprises a source of pressurized hydraulic fluid (such source can include a sump or another suitable reservoir and a pump which draws fluid from the sump and supplies pressurized fluid to one or more conduits), a fluid-operated torque sensor including rolling elements arranged to apply to the flanges of the one pulley the entire torque to be transmitted by the transmission, and means for supplying fluid to the at least one unit. Such supplying means comprises at least one adjustable regulating valve, and the torque sensor comprises rolling elements and components having faces which define for the rolling elements paths for movement to adjust the at least one pressure regulating valve in response to changes of the torque being supplied to the shaft of the first pulley.
The rolling elements can be, and normally are, spheres.
The at least one pressure regulating valve can include one or more ports provided in the shaft of the one pulley, and a valving element forming part of the piston of the aforementioned cylinder and piston unit and being movable axially of the shaft of the one pulley to thereby vary the rate of fluid flow between a plenum chamber which is defined by the cylinder and piston unit and the one or more ports in the periphery of the shaft forming part of the respective pulley. The valving element of the piston can comprise a sleeve-like portion which sealingly or substantially sealingly engages the peripheral surface of the respective shaft and is movable axially of such shaft to a plurality of axial positions in each of which it overlies the port or ports to a different extent. The port or ports communicates or communicate with one or more channels in the shaft of the respective pulley.
The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved continuously variable transmission itself, however, both as to its construction and the modes of assembling, installing and operating the same, together with numerous additional important and advantageous features and attributes thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawings.